Is there any basis in Islam for Zarqawi's statement that innocent Muslims can be killed during jihad?
Zarqawi declared that previously he had called off attacks on the “enemy” because of the risk of harming innocents, but now he had permission from some scholars that he could launch attacks on the “enemy” even if it resulted in some incidental innocent civilian casualties. This is similar to the justification for incidental civilian deaths as a result of military air strikes on targets inside populated, residential areas, that if in attacking the enemy, it is permissible to do so even if some civilian casualties are expected..
Based on the Quran and Hadith, it is not permissible in Islam to kill innocents even in the heat of battle on a battlefield. This implies that it is not permissible to use weapons like bombs and missiles which have a high probability of causing incidental civilian casualties. No reputable scholar of Islam would agree with such tactics even in war, so whoever the scholars are who gave him permission are singularly incompetent or motivated by other things. It is not unknown for scholars of extremist sects in Christianity to hold twisted views and interpretations, for example, White Christian Supremacists, and these rogue scholars may be their Muslim equivalents.
Zarqawi's declaration is so contrary to basics of Islam that even a non-Muslim like Lt. Gen. John Abizaid, who is not a Muslim scholar, can repudiate it. It is so ridiculous that it is not taken seriously by Muslims, except perhaps by his small band of misguided and brain-washed followers.